MIAMI — The San Antonio Spurs agonized all offseason and even during the season over last year's crushing NBA Finals loss to the Miami Heat.

A focused, one-year march to redemption is nigh for the Spurs.

In another basketball clinic, the Spurs schooled the Heat 107-86 and took a 3-1 series lead.

Game 5 is Sunday in San Antonio (8 p.m. ET, ABC), and the Spurs are on the verge of the franchise's fifth championship and first since 2007. The Spurs were 26 seconds from a title last season but blew a five-point lead with 28.2 seconds left in the fourth quarter of Game 6.

OK, so the Spurs didn't make 19 of their first 21 shots like they did in Game 3. Still, it was offensive harmony, and the Spurs made 11 of their first 18 shots, grabbing an early lead that that extended to 31-17 with 10:24 left in the second quarter.

"I'm pleased that they performed as well as they did while we've been in Miami, and that's about as far it goes," Spurs coach Gregg Popovich said. "Now, we've got to go back home and play as well or better."

It was 55-33 with 1:07 left in the first half, and the Heat trailed by 20 points in the second quarter for the second time in the past two games. The Spurs were up 81-57 after three quarters, and LeBron James was the only Heat player with more than eight points headed into the fourth quarter.

The Spurs ball movement had the Heat scrambling to defend open shooters. Nine Spurs scored in the first half, and it was too difficult for the Heat to cover Kawhi Leonard (20 points and 14 rebounds), Tony Parker (19 points), Boris Diaw (eight points, nine rebounds and nine assists) and Patty Mills (14 points).

HIGHLIGHTS: Spurs win big in Game 4

There Spurs won the last two games without major scoring production from Tim Duncan (10 points, 11 rebounds) and Manu Ginobili (seven points).

"They just played great and I can honestly say I don't think any of us were expecting this kind of performance," Heat coach Erik Spoelstra said. "They were great. You have to give them credit for that. We just couldn't get into a rhythm on either side of the ball, and it went from there."

But it just wasn't offense. The Spurs made it difficult for the Heat, who shot 35.3% and had trouble finishing in the paint in the first half, to score. James scored 28 points, and the combined 22 points from Dwyane Wade and Chris Bosh were meaningless.

"Ours heads are a little down right now. … It's just human nature, but we still have to go out and play on Sunday," James said. "They smashed us two straight home games. Got off to awful starts. They came in and were much better than us in these two games. It's that simple."

It will take an epic collapse for the Spurs to fritter this lead. No team has come back from a 3-1 deficit and won the Finals, and the Spurs have at least one more game at home.

It is the first time the Heat have trailed a series by two games since losing the 2011 Finals 4-2 to the Dallas Mavericks.

In a game the Heat needed, they were again outworked and outhustled. Even what Heat coach Erik Spoelstra called a painful video review of Game 3, the Heat were not any better in Game 4.

Many of the same issues from the last game were a problem in this game: inability to stop the Spurs' offense or break down their defense.

Another major difference right now between the two teams from a year ago? San Antonio improved and Miami did not. Miami's depth has been exposed, and the grind of playing in four consecutive Finals and trying to win three straight titles is catching up with the Heat who hadn't lost at home in the 2014 postseason until this series.